1. Field of the Invention
This invention relates to the preparation of new oxadiazole derivatives useful in the control of parasites, especially endoparasites.
Parasitic infections of man and animals present a considerable health hazard. Due to their widespread occurrence attempts to find cures for these infections has led to considerable research seeking to find agents which are effective in their control. One parasite of man which is particularly widespread in certain parts of the world is Entamoeba histolytica. This parasite generally inhabits the gut and frequently results in death of the host, especially when infestation of the liver occurs in later stages of the infection. In animals such as sheep and cattle, various helminths are also well-known to give rise to a considerable health hazard.
2. Summary of the Invention
We have now found that certain oxadiazole derivatives hereinafter set forth have particularly high action against a variety of parasites.
The invention provides a compound selected from the group consisting of i) a compound of formula ##STR3## in which A is selected from the group consisting of residues of formula ##STR4## R.sup.1 and R.sup.2 are each selected from the group consisting of a hydrogen atom, a halogen atom and a methyl or ethyl group and where R.sup.3 is selected from the group consisting of a phenyl and a thienyl group and such group substituted by at least one substituent selected from the group consisting of halogen, azido, cyano, C.sub.1 -C.sub.5 alkyl, C.sub.1 -C.sub.5 alkoxy, trifluoromethyl, C.sub.1 -C.sub.5 alkylthio, C.sub.1 -C.sub.5 alkylsulfinyl, C.sub.1 -C.sub.5 alkylsulfonyl, thiocyanato, nitro, amino and hydroxy; and
ii. a compound of the formula ##STR5## in which D is selected from the group consisting of residues of the formula ##STR6## in which R is selected from the group consisting of amino, vinyl, allyl, ethynyl, C.sub.1 -C.sub.5 alkyl, C.sub.1 -C.sub.5 alkoxy, C.sub.1 -C.sub.5 alkylthio or a C.sub.1 -C.sub.5 alkyl group substituted by at least one halogen atom, where R.sup.1 and R.sup.2 have the above defined meaning, and R.sup.4 is a phenyl group substituted by at least one substituent selected from the group consisting of cyano, alkoxy of 1-3 C atoms, hydroxy, mercapto, sulfo, thiocyanato, and a group of formula --SO.sub.x R.sup.5 in which x is 0 or the integer 1 or 2 and R.sup.5 is (C.sub.1 -C.sub.5) alkyl;
As will appear hereinafter various compounds of formula I are also useful intermediates for the preparation of other compounds of the said formula.